The invention pertains to the area of chelate preparation in a non-aqueous environment.
Organic acid chelated transition metals are used as an important trace mineral source for human and animal applications. Certain metal ions are also known to be beneficial in stimulating plant growth and in the production of larger, stronger plants, and for increasing the production of fruits and vegetables. It has become generally accepted that the chelated forms of metals with organic acids are better assimilated by plants, animals, and human beings than are metal salts.
Plant, animal and human tissues show increased metal content when exposed to metal organic acid chelates. Metal organic acid chelates common in the prior art result from reacting a metal ion from a soluble metal salt with an organic acid or its salt; with a mole ratio of one mole of metal to one to three moles (depending on the valency and coordination number of the metal ion) of organic acid to form coordinate covalent bonds.
Organic acid chelates have been generally made in the prior art by reaction using either amino acids, picolinic, nicotinic acids, or hydroxycarboxcylic acids.
Amino and other organic acid chelates are products which result from the reaction of organic acids and a metal ion in the form of either an oxide, hydroxide or salt. In the prior art, for example, amino acid chelates have generally been made by the reaction of one or more amino acids, dipeptides, and polypeptides or protein hydrolisate ligands in an aqueous environment under appropriate conditions which will cause the interaction between the metal and amino acids to form an amino acid chelates.
Metal picolinates are synthesized by the reaction of a metal salt with a picolinic acid salt such as sodium, potassium or ammonium picolinate in a water solution.
Hydroxycarboxcylic acids such as calcium or magnesium citrates are synthesized by the reaction of citric acid with calcium or magnesium oxide, hydroxide or a carbonate water suspension.
Patents indicative of the prior art are U.S. Pat. No. 4,315,927 issued to Evans; U.S. Pat. No. 4,814,177 issued to Walsdorf; U.S. Pat. Nos. 4,830,716 and 4,599,152 issued to Ashmead; U.S. Pat. No. 5,504,055 issued to Hsu; and U.S. Pat. No. 5,516,925 issued to Pedersen. These prior art methods teach the production of metal organic acid chelates produced from either a water solution or paste having a high water content.
Metal organic acid chelates may also be produced in the form of a dry product by some means of drying. As it is well known for those skilled in the art, drying may be accomplished by fluid bed, rotary drum, steam tube, spray, or tray dryer. Drying itself is an energy consuming procedure, technically complicated, and requiring sophisticated equipment. In the case of drum drying, to obtain a final product which is a fine powder, it is also necessary to mill the product exiting the drum.
Organic acid chelates are made by reacting an organic acid ligand with a metal compound selected from the group consisting of metal oxides, metal hydroxides and metal salts in a non aqueous environment where the quantity of organic acid ligand used corresponds at least to the stoichiometry requirements of the desired metal organic acid chelate to be produced. The chelate is recovered from the suspension by means of filtration or evaporation of the liquid portion of the suspension.
The present invention eliminates the disadvantages associated with producing organic acid chelates in an initial aqueous environment and describes a method for producing metal organic acid chelates in a substantially non-water media.
The reactants for this process include an organic acid ligand, and a metal compound such as metal oxides, hydroxides, or salts. The organic acid ligand and metal compound are then immersed in a non-aqueous liquid such as, for example, methanol, ethanol, i-propanol, hexane, petroleum ether, etc. and thereafter mixed at room or elevated temperature for a sufficient period of time to allow the reactants to form the desired chelate product.
In some cases, for example, when the non-aqueous liquid used is methanol or other alcohols, the reaction of the organic acid ligand with a metal compound will form a water by-product which will then remain as part of the alcohol solution or solvent.
In other cases, for example, when the non-aqueous liquid used is hexane or petroleum ether, the reaction of the organic acid ligand with a metal compound will also form a water by-product but which may be removed from the reaction media using a Dean Stark water separator or other similar equipment.
The reactants, and their reaction products, i.e. metal organic acid chelates, are highly polar chemical compounds that are insoluble in non-polar organic liquids and form suspensions when added to the non-polar organic liquids. Water is also a reaction product but as described in the preceding paragraphs, can be either removed by water separation equipment or becomes part of the non-aqueous solution; effectively reducing the strength of the alcohol solution to some extent. Therefore, using an organic liquid, rather than water, permits quantitative removal of the metal organic acid chelate produced from the reaction media by simple filtration.
It is well known in the art that organic liquids contain water to some degree and that as used in this specification organic liquids mean substantially water-free liquids and not 100% water free.
Additionally, because both the reactants and products are insoluble in an organic liquid, the liquid may be reused after filtration of the suspension for subsequent metal organic acid chelate synthesis. Furthermore, organic liquid tends to be volatile so the liquid can be removed or separated from the reaction products either by filtration or by drying the chelate either in an open air environment or under vacuum at room temperature.
The metal organic acid chelate product, when allowed to dry, has the physical characteristic of a very fine powder, which does not require subsequent milling.
Metal compounds used in my process can include, but should not be limited to, oxides such as calcium oxide and magnesium oxide; hydroxides such as copper hydroxide, zinc hydroxide, ferrous hydroxide, manganese hydroxide, cobalt hydroxide, and chromium hydroxide; salts such as ferrous sulfate, manganese sulfate, cobalt chloride, and chromium chloride.
Other salts, complexes and chelates of Ca, Mg, Mn, Cu, Zn, Co, Cr, K, Fe and other metals of interest can be mixed with appropriate amounts of citric acid, ascorbic acid, picolinic acid, nicotinic acid, glycine, lysine, glutamic or other organic acids, dipeptides, polypeptides and protein hydrolizates in a non-aqueous liquid such as methanol, i-propanol, hexane, or other non water organic liquid to obtain the desired chelate product which does not require milling subsequent to extraction from the suspension.
The above described method for synthesizing metal organic acid chelates does not require specific sophisticated equipment for drying and milling; therefore, less energy is required for the manufacturing process. The process permits multiple use of the non aqueous liquid, does not produce any waste products, and is environmentally safe.
The following are examples of metal organic acid chelates produced according to my invention. In each example heat is used to boil the suspension. This is done to increase the reaction rate of the process. However, it is not necessary to heat to boiling and furthermore, no heat is necessary for any other reason but to increase the reaction rate.